The train is running on the rails.
curtain rail; sliding door track
Used for rails or tracks for curtains, sliding doors, drawers, etc.
I install a curtain rail.
groundwork; preparations; arrangements
Figurative use, often in the phrase レールを敷く (to lay the groundwork).
For the project's success, we need to lay the groundwork in advance.
Construction began to lay track for the new rail line.
It's not good for parents to lay out their child's future path in advance.
He deviated from life's expected track and pursued his own path.
The train was running slowly along the rails.
軌道 is a more technical term that can mean railway track or an orbit, whereas レール is the everyday word for the physical rail bars.
book; volume; script · this; present; current; in question · main; head; principal · real; genuine; regular; proper · counter for long cylindrical objects; counter for films, TV shows, etc.; counter for goals, home runs, etc.; counter for telephone calls
monorail
guardrail
grooved rail
railgun
rail bus
Loanword from English 'rail'.
long rail
curtain rail
picture rail